This invention relates to methods and apparatus for fluid distribution systems and, more particularly, to an improved pulse irrigation system that is more adaptable to varied needs and which, more uniformly, distributes irrigating fluids with reduced fluid wastage.
There is an unquestionable need for better irrigation systems than those which are generally available to the industry. For example, a typical system has a manifold that is coupled to a water supply. Each line is connected to the manifold through a respective pilot valve. Each of these lines comprises a set of elastic tubes, each of the tubes being joined to the next tube in the series through a combination diaphragm valve and discharge nozzle. The elastic tubes expand slightly under hydraulic pressure as they fill with irrigating water until the pressure at the end of the line approaches the supply pressure. When that pressure is reached, a pilot valve trips to stop the filling and cause the individual diaphragm valves to block the passageways to the manifold and open passageways to the discharge nozzles in each of the diaphragm valves. The irrigating water is sprayed from the nozzles and, when the water stored under pressure in the communicating elastic tubes is sufficiently depleted, the diaphragms in each of the valves shift position in response to the header pressure to block any further flow from the discharge nozzles and permit the elastic tubes to fill once more in order to repeat the cycle.
This closed loop system, however, has a number of serious deficiencies. The inherent limitations of this system, for example, prevent its application to larger installations. A ten acre orchard, for instance, would require forty or fifty irrigating loops because the time needed to fill each loop limits the number of emitters that can be inserted in a loop to forty or fifty emitters. Operation of each of these loops also must be synchronized which is a burdensome task. Further, the proliferation of these loops aggravates the problem of wasted pilot valve discharge water. The quantity of fluid discharged from each nozzle and uneven pressure distribution at these nozzles in these systems, moreover, varies and thus fail to supply uniform charges of irrigating water. This problem of providing uniform charges of irrigating fluid is made even more difficult when the system is installed in hilly terrain, in which the static pressure head changes depending on the relative elevation of the line. This variation in discharge makes the system almost impossible to use for distributing chemicals with the irrigating water because of the non-uniform nature of the quantity of fertilizers, herbicides and the like that are discharged through the nozzles. These discharge nozzles also have very small passageways and thick relatively inflexible diaphragms that tend to clog with entrained particulate matter and produce increased flow resistance, even when unclogged.
Further in this regard, the use of interconnecting elastic tubes as fluid reservoirs is quite inadequate. The elastic deformation of these tubes, and hence the water volume accumulated in each cycle, is limited to some value that is less than the force required to rupture the coupling between each end of the elastic tube and the fittings on the valves to which these tubes ends are connected. This limit on tube deformation imposes a small storage volume which requires only a short filling time, the result of which is an undesirably rapid operating cycle with low discharge volume. These high cycle rates are not acceptable in many applications and aggravate the pilot valve waste water problem.
Pilot valves, which initiate irrigating flow through the discharge nozzles, discharge into the atmosphere and, as a consequence, are responsible for a loss of water in the valve vicinity. Not only does this characteristic waste valuable water because the water is discharged in a place that cannot use it for irrigation purposes, but it also produces potentially more serious effects. For example, the pilot valve wastage usually is dispersed underground. This dispersion requires additional pumping power and water; a sub-soil dispersion system to avoid soil saturation and water ponding; and it concentrates herbicides, fertilizers and the like at the dispersion sites.
As a further deficiency, systems of this nature require a uniform number of discharge nozzles and associated diaphragm valves in each line loop. This requirement produces an irrigation system that can be used only in farms and orchards with an essentially rectangular shape. Acreage, however, freqently comes in irregular shapes. There are other, very practical considerations that have detracted from the value and utility of prior art apparatus. Illustratively, for ground installed emitters in fruit orchards, the upwardly protruding plastic nozzle on some designs frequently is stepped on and broken by laborers. These emitters also must be drained of water before cold weather occurs, a laborious task, or ice formation within the emitters will break the valves.
There are some proposed systems in which the irrigation lines are not closed loops but are, instead, a sequence of ducts and valves that form a linear network. Proposals for these systems, however, are not entirely satisfactory because the valves not having a self-cleaning action, are vulnerable to clogging and stoppages from dirt and other particulate matter entrained in the irrigating fluid. Further in this regard, these arrangements limit the number of parallel lines that can be serviced in a particular system and increase the volume of irrigating fluid that is wasted through discharge to the atmosphere with each pulse from the pilot valve. There is even an additional source of waste water during transition from one valve position to another because the inlet and discharge ports both remain open when the valve is in transition.
Thus, there is a need for an improved irrigation method and apparatus that provides a uniform pressure distribution and volume of irrigating fluid discharge from each nozzle; a more acceptable cycle rate; greater fluid storage volume in the elastic tubes between the diaphragm valves and discharge nozzle combinations in which the elasticity is selected to satisfy emitter flow requirements rather than being limited to the gripping force needed to keep the tube secured to the adjacent emitters; a pulser valve that does not waste irrigating water and a system of irrigating lines that do not require the same number of nozzles in each line but can be varied in number and in length to match the irrigation system to the shape of the acreage that is being cultivated. There are, of course, the further needs to avoid particulate matter clogging and vulnerability to damage not only through field abuse, but also from ice formation.